Cationic block polymer agglomeration agents for mineral bearing ores

ABSTRACT

A process for the percolation leaching of minerals from a mineral-beating ore comprises agglomerating the mineral-bearing ore with an agglomerating agent of a cationic block copolymer having a polymeric segment and a block containing an ammonium cation optionally with a block derived from an acrylamide monomer, forming the ore/agglomerating agent mixture into a heap, and leaching the heap by percolation with a leaching solution for subsequent recovery of the minerals at an acidic pH.

This application is a continuation-in-part of application Ser. No.08/301,454 filed Sep. 6, 1994, now U.S. Pat. No. 5,512,636.

FIELD OF THE INVENTION

The present invention relates to agglomerating agents applied to mineralbearing ores to be subjected to leaching recovery operations. Theagglomerating agents of the present invention aid in the agglomerationof mineral bearing ore containing fines to allow effective heap leachingfor mineral recovery.

BACKGROUND OF THE INVENTION

In recent years, the use of chemical leaching to recover minerals fromlow grade mineral bearing ores has grown. For example, caustic cyanideleaching is used to recover gold from low grade ores having about 0.02ounces of gold per ton and dilute sulfuric acid is used to recovercopper from copper bearing ores. Such leaching operations are typicallycarried out in large heaps. The mineral bearing ore from an open pitmine, or other source, is crushed to produce an aggregate that is coarseenough to be permeable in heaps but fine enough to expose the mineralvalues to the leaching solution. After crushing, the ore is formed intoheaps on impervious leach pads. The leaching solution is evenlydistributed over the top of the heaps by sprinklers, wobblers, or othersimilar equipment. As the barren leaching solution percolates throughthe heap, it dissolves the minerals contained in the ore. The liquorcollected by the impervious leach pad at the bottom of the heap isrecovered and this "pregnant solution" is subjected to a mineralrecovery operation. The leachate from the recovery operation is held ina barren pond for reuse.

Economical operation of such heap leaching operations requires that theheaps of crushed ore have good permeability after being crushed andstacked so as to provide good contact between the ore and the leachate.Ores containing excessive quantities of clay and/or fines (i.e., 30% byweight of ⁻ 100 mesh fines) have been found undesirable due to theirtendency to slow the percolation flow of leach solution. Slowing of thepercolation flow of the leach solution can occur when clay and/or finesconcentrate in the center of the heap while large rock fragments tend tosettle on the lower slopes and base of the heap. This segregation isaggravated when the heap is leveled off for installation of thesprinkler system that delivers the leach solution. This segregationresults in localized areas or zones within the heap with markeddifference in permeability. The result is channeling where leachsolution follows the course of least resistance, percolating downwardthrough the course ore regions and bypassing or barely wetting areasthat contain large amounts of clay and/or fines. Such channelingproduces dormant or unleached areas within the heap. The formation of a"slime mud" by such fines can be so severe as to seal the heap causingthe leach solution to run off the sides rather than to percolate. Thiscan require mechanical reforming of the heap. The cost of reforming theheaps which can cover 160 acres and be 200 feet high negates theeconomies of scale that make such mining commercially viable.

In the mid 1970s, the United States Bureau of Mines determined that orebodies containing high percentages of clay and/or fines could be heapleached if the fines in the ore could be agglomerated. The Bureau ofMines developed an agglomeration process in which crushed ore is mixedwith Portland cement at the rate of from 10 to 20 pounds per ton, wettedwith 16 to 18% moisture (as water or leach solution), agglomerated by adisk pelletizer and cured for a minimum of eight hours before beingsubjected to stacking in heaps for the leaching operation.

In commercial practice, the method developed by the United States Bureauof Mines has not met with widespread acceptance because of the cost andtime required. However, the use of cement, as well as other materials,as agglomerating agents is known. Agglomerating practices tend to besite specific and non-uniform. Typically, the action of the conveyorswhich move the ore from the crusher to the ore heaps or the tumbling ofore down the conical piles is relied on to provide agglomeration for amoistened cement-ore mixture. Lime has been found to be less effectivethan cement in controlling clay fines, it is believed this is becausethe lime must first attack the clay lattice structure in order toprovide binding.

Cement has been found to be most effective in high siliceous ores(crushed rock) and noticeably less effective in ores having a high claycontent. The large volumes of cement required also present problems. Thetransportation to and storage of large volumes of dusty cement at theoften remote mine locations is difficult. With the growth of such miningmethods, the need for cost effective, efficient agglomerating materialshas grown.

U.S. Pat. Nos. 5,077,021 and 5,077,022 disclose agglomerating agents andmethods for use in heap leaching which comprise anionic polymers ofacrylamide and acrylic acid.

U.S. Pat. No. 4,875,935 discloses a method for extracting copper fromcopper minerals which employs an agglomerating agent comprising anionicacrylamide polymers containing at least five mole percent of carboxylateor sulfonate groups. U.S. Pat. Nos. 4,898,611 and 5,100,631 discloseimprovements in the agglomeration of a gold or silver ore with cementcomprising including specific water soluble vinyl polymers in the cementagglomeration treatment.

U.S. Pat. Nos. 5,112,582 and 5,186,915 disclose agglomerating agents andmethods for using heap leaching of mineral bearing ores which comprisesan anionic polymer of acrylamide and acrylic acid and sufficient time toprovide a pH of from about 9.5 to 11.

SUMMARY OF THE INVENTION

The present invention is directed toward new and improved agglomeratingagents for use in heap leaching of mineral bearing ores. Morespecifically, the present invention is directed toward a newagglomerating agent comprising cationic polymers. The cationic polymersmay be used in combination with cement or lime. The agglomerating agentof the present invention may be employed in acidic or alkaline leachingoperations. Preferably, the agglomerated agents of the present inventionare cationic graft copolymers, cationic block copolymers or cationiccopolymers of acrylamide and diallyl dimethyl ammonium chloride(DADMAC). It was discovered that such cationic polymers alone or incombination with cement or lime are effective agglomerating agents inacidic or alkaline heap leaching operations.

The effectiveness of the agglomerating agents of the present inventionwas determined in submersion/dispersion testing at low pH (pH 2.0) andhigh pH (pH 10.7). The submersion/dispersion test measures the weight offines washed from an agglomerate after a three minute submersion period.The water used in the tests was pH adjusted using sulfuric acid (pH 2.0)and lime (pH 10.7) for the acidic and alkaline tests respectively. Thesamples to be tested were agglomerated in a laboratory drum typeagglomerator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides a new agglomerating agent for use in heapleaching of mineral bearing ores. It has been discovered that cationicgraft copolymers, cationic block copolymers and cationic copolymers ofacrylamide and DADMAC are effective agglomerating agents under bothacidic and alkaline conditions. The cationic copolymers can be used incombination with known agglomerating agents such as cement or with pHcontrol agents such as lime.

To allow comparison of the efficiency of the agglomerating agents of thepresent invention when applied to different ores, standardized testingprocedures were developed. These procedures allow the efficiency of thevarious agglomerating agents to be compared. The standardized proceduresbegin with preparation of the ore to be tested. As received gold bearingore was air dried and sieved to two size factors: 1/2 inch by 1/4 inch,and ⁻ 16 mesh. Test samples totaling 500 grams were prepared bycombining 350 grams of the 1/2 by 1/4 inch material with 150 grams ofthe ⁻ 16 mesh material. As received copper ore was air dried and sievedto ⁻ 1/2 inch. The ⁻ 1/2 inch material was riffled into 500 gram testsamples.

The 500 gram test samples were agglomerated in a laboratory drum typeagglomerator. 10% moisture addition was used in agglomerating the goldbearing ore, 15% moisture addition was used in agglomerating the copperbearing ore. Testing was conducted under both acidic and alkalineconditions. Acidic conditions were obtained by making down thetreatments in water adjusted to a pH of 2.0 with sulfuric acid. Alkalineconditions were obtained by making down the treatments in water adjustedto a pH of 10.7 with lime. Under alkaline conditions, lime or cement wasadded to the mineral bearing ore to provide alkalinity. The treatmentsolutions were added to the dry mineral bearing ore with a syringe pumpas it was rotating in the drum. Total agglomeration time was fiveminutes.

After agglomeration, the mineral bearing ore was dried on a 10 meshsieve for 24 hours at 20° C. and 50% relative humidity. After drying,the samples were subjected to submersion/dispersion testing. Thesubmersion/dispersion testing measures the weight of fines washed fromthe agglomerates after a 3 minute submersion. The water used forsubmersion was pH adjusted, using sulfuric acid (pH 2.0) and lime (pH10.7) for the acidic and alkaline tests respectively.

The agglomeration agents of the present invention comprise cationiccopolymers. The cationic copolymers are graft copolymers, blockcopolymers, or linear copolymers of acrylamide and diallyldimethylammonium chloride (DADMAC). Polymers with long sequences of two monomerscan be categorized as block copolymers or graft copolymers. In graftcopolymers sequences of one monomer are "grafted" onto a "backbone" ofthe second monomer type, ##STR1##

In block copolymers, synthesis may be controlled to form a copolymerhaving long sequences of monomers, e.g. A and B, as follows:

    -AAAA-BBBB-AAAAA-BBBBB-.

Graft Copolymers

The graft polymers of the present invention contain polymeric segmentsobtained from the polymerization of acrylamide and cationic monomerswhich are attached or "grafted" to another polymer chain which iscomprised of the repeating units of one or more monomers. The resultinggraft copolymers are soluble in an aqueous medium.

The graft copolymer of the invention has the general structure: ##STR2##wherein E in the above formula (Formula I) is the repeat unit obtainedafter polymerization of an α, β ethylenically unsaturated compound,preferably carboxylic acid, amide form thereof, alkyl (C1-C8) ester orhydroxylated alkyl (C1-C8) ester of such carboxylic acid. Compoundsencompassed by E include the repeat unit obtained after polymerizationof acrylamide, methacrylamide, acrylic acid, methacrylic acid, maleicacid or anhydride, styrene sulfonic acid, 2-acrylamido-2-methylpropylsulfonic acid, itaconic acid, and the like. Ester derivatives of theabove mentioned acids such as 2-hydroxypropyl acrylate, methylmethacrylate, and 2-ethylhexyl acrylate, are also within the purview ofthe invention.

The molar percentage of a:b is from about 95:5 to 5:95, with the provisothat the sum of a and b equals 100%,

G in the above formula (Formula I) is a polymeric segment comprisingrepeat units having the structure: ##STR3## wherein R₁, R₂ and R₃ inFormulae I and II are the same or different and are hydrogen or a loweralkyl group having C₁ to C₃. F in the above formula is a salt of anammonium cation, such as NHR₃ N⁺ R(₄,5,6)M⁻ or OR₃ N⁺ R(₄,5,6)M⁻,wherein R₃ is a C₁ to C₄ linear or branched alkylene group, and R₄, R₅and R₆ can be selected from the group consisting of hydrogen, C₁ to C₄linear or branched alkyl, C₅ to C₈ cycloalkyl, aromatic or alkylaromaticgroup; and M is an anion, such as chloride, bromide, or methyl orhydrogen sulfate. Typical cationic monomers are2-acryloyloxyethyltrimethylammonium chloride (AETAC),3-methacrylamidopropyl-trimethylammonium chloride (MAPTAC),2-methacryloyloxyethyltrimethylammonium chloride (METAC) anddiallyldimethylammonium chloride (DADMAC), etc.

It is to be understood that more than one kind of cationic monomer maybe present in Formula II.

The molar percentage c:d in Formula II may vary from 95:5 to 5:95, withthe proviso, however, the sum of c and d equals 100%.

There is no limit to the kind and mole percent of the monomers chosen solong as the total adds up to 100 mole % and the resulting copolymers arewater soluble.

At present, the preferred water soluble graft copolymer for use as amineral oil agglomerating agent is: ##STR4##

The molar percentage of a:b is from about 95:5 to 5:95, with the provisothat the sum of a and b equals 100%. G in Formula III is: ##STR5##

Monomer d is 2-acryloyloxyethyltrimethylammonium chloride (AETAC). Themolar percentage c:d in the polymer segment G (Formula IV) is the ratioof acrylamide:AETAC. It may fall within the range between 95:5 and 5:95.The sum of c and d must add up to 100%.

The number average molecular weight (Mn) of the polymeric segment G isnot critical and may fall within the range of 1,000 to 1,000,000.Preferably, the number average molecular weight will be within the rangeof 5,000 to 500,000, with the range of about 10,000 to about 200,000being even more desirable. The key criterion is that the resulting graftcopolymer be water soluble. A method of preparing the graft copolymersof the present invention is set forth in U.S. Pat. No. 5,211,854,incorporated herein by reference.

Block Copolymers

The block copolymers of the invention useful for mineral oreagglomeration contain a polymeric segment obtained from polymerizationof hydrophobic or water insoluble monomers attached to a polymer chainobtained from polymerization of one or more water soluble monomers. Theresulting block copolymers are water soluble.

The block copolymers of the present invention have the generalstructure: ##STR6## wherein J is a polymeric segment obtained from thepolymerization of hydrophobic or water insoluble monomers. Examples ofsuch monomers include alkyl acrylamides, alkyl methacrylamides, alkylacrylates, alkyl methacrylates, and alkylstyrenes. Preferably, thehydrophobic monomer is an alkyl acrylate having 4 to about 16 carbonatoms in the alkyl group such as 2-ethylhexyl acrylate. Other suitablehydrophobic or water insoluble monomers include the higher alkyl estersof ethylenically unsaturated carboxylic acids such as alkyl dodecylacrylate, dodecyl methacrylate, tridecyl acrylate, tridecylmethacrylate, octadecyl acrylate, octadecyl methacrylate, ethyl halfester of maleic anhydride, diethyl maleate, and other alkyl estersderived from the reactions of alkanols having from 8 to 20 carbon atomswith ethylenically unsaturated carboxylic acids such as acrylic acid,methacrylic acid, maleic anhydride, fumaric acid, itaconic acid andaconitic acid, alkylaryl esters of ethylenically unsaturated carboxylicacids such as nonyl-α-phenyl acrylate, nonyl-α-phenyl methacrylate,dodecyl-α-phenyl acrylate and dodecyl-α-phenyl methacrylate; N-alkyl,ethylenically unsaturated amides such as N-octadecyl acrylamide,N-octadecyl methacrylamide, N,N-dioctyl acrylamide and similarderivatives thereof; vinyl alkylates wherein alkyl has at least 8carbons such as vinyl laurate and vinyl stearate, vinyl alkyl etherssuch as dodecyl vinyl ether and hexadecyl vinyl ether; N-vinyl amidessuch as N-vinyl lauramide and N-vinyl stearamide; and aralkylstyrenessuch as t-butyl styrene. Of the foregoing hydrophobic monomers, thealkyl esters of acrylic acid and methacrylic acid wherein alkyl has from4 to 16 carbon atoms, are preferred.

Monomer x, when present, in the Formula V is a nonionic monomer such asacrylamide or alkylacrylamide. R₄ and R₅ is H or a lower alkyl grouphaving C₁ to C₃. Monomer y is a cationic monomer. K in the above formulais a salt of an ammonium cation, such as NHR₆ N⁺ R₇,8,9 M⁻ or OR₆ N⁺R₇,8,9 M⁻, wherein R₆ is a C₁ to C₄ linear or branched alkylene group,and R₇, R₈ and R₉ can be selected from the group consisting of hydrogen,C₁ to C₄ linear or branched alkyl, C₅ to C₈ cycloalkyl, aromatic oralkylaromatic group; and M⁻ is an anion, such as chloride, bromide, ormethyl or hydrogen sulfate. Typical cationic monomers are2-acryloxyethyltrimethyl ammonium chloride (AETAC),3-methacrylamidopropyltrimethyl ammonium chloride (MAPTAC),2-methacryloxyethyltrimethyl ammonium chloride (METAC) and diallyldimethyl ammonium chloride (DADMAC), etc.

The molar percentage x:y of nonionic monomer:cationic monomer, may fallwithin the range of between 0:100 to 95:5. The molar percentages of xand y must add up to 100%. It is to be understood that more than onekind of cationic monomer may be present in the Formula V.

At present, the preferred water soluble block copolymer is: ##STR7##wherein PEHA is poly(2-ethylhexyl acrylate). The number averagemolecular weight (Mn) of poly(EHA) may fall within the range of 500 to1,000,000. Preferably, the number average molecular weight will bewithin the range of 1,000 to 500,000, with the range of about 5,000 toabout 200,000 being even more desirable.

In this invention, the preferred monomer x is acrylamide and monomer yis 2-acryloxyethyltrimethyl ammonium chloride (AETAC). The molarpercentage of x:y is from about 0:100 to 95:5, with the molar percentageof from about 10:90 to 75:25 being preferred. A method of preparing thex-y copolymers of the present invention is disclosed in U.S. Pat. Nos.3,284,393, Reissue 28,474 and Reissue 28,576, herein incorporated byreference. A method of preparing the block copolymer of the presentinvention is disclosed in U.S. Pat. Nos. 5,182,331 and 5,234,604.

Linear Acrylamide/Diallyl Ammonium Chloride

Diallyl dimethyl ammonium chloride (DADMAC) is a quaternary monomerwhich, when polymerized, yields cationic water soluble polymers.

The copolymerization of acrylamide with DADMAC by a water-in-oilemulsion process is known in the art. For instance, U.S. Pat. No.3,920,599 discloses the process of preparing the homopolymer of DADMACand DADMAC/acrylamide copolymers by using 2,2-azobis(isobutyronitrile),benzoyl peroxide, and or lauroyl peroxide.

U.S. Pat. No. 3,968,037 teaches the use of t-butylperoxypivalate topolymerize DADMAC in emulsion.

U.S. Pat. Nos. 4,077,930 and 4,147,681 disclose a process to prepareacrylamide/DADMAC emulsion by using at least 20% by weight, based on theweight of the oil phase, of an emulsifier having HLB (hydrophilelipophile balance) of at least 7.

U.S. Pat. No. 4,439,580 discloses use of free radical initiators such asorganic peroxy initiators, redox systems, and azo initiators, i.e.,4,4-azobis-4 cyanopentoic acid and 2,2-azobis (isobutyronitrile) topolymerize DADMAC in emulsion. The preferred initiator is ammoniumpersulfate (column 3, lines 24-31).

U.S. Pat. No. 4,864,007 discloses the utilization of a cationic azoinitiator (water soluble) and phosphorous acid or a derivative asregulator to polymerize DADMAC.

In practice, bench scale testing will allow selection of the mosteffective cationic copolymer and cement or lime. Such testing ispreferred because it was discovered that efficiency was somewhatinfluenced by the composition of the ore to be treated. Typicaltreatment rates for cationic polymers range from about 0.05 to about2.0, preferably about 0.1 pounds active per ton of ore. The cement orlime can be added at treatment rates of from about 1 to 20 pounds perton of ore.

Testing of a variety of commercially available polyvinyl alcohols,polyethylene oxides, cationic copolymers, and a commercial anionicpolymer agglomerating agent in accordance with U.S. Pat. Nos. 5,077,021and 5,077,022 was undertaken. Table I summarizes the treatments tested.

                  TABLE I                                                         ______________________________________                                        Treat-                                                                        ment  Trade Name   Description                                                ______________________________________                                        A     Airvol 107   Polyvinyl alcohol, low M.W., fully                                            hydrolyzed                                                 B     Airvol 165   Polyvinyl alcohol, high M.W., super                                           hydrolyzed                                                 C     Airvol 205   Polyvinyl alcohol, low M.W., partially                                        hydrolyzed                                                 D     Airvol 350   Polyvinyl alcohol, high M.W., fully                                           hydrolyzed                                                 E     Vinol 540    Polyvinyl alcohol, high M.W., partially                                       hydrolyzed                                                 F     Polyox WSR-N-10                                                                            Polyethylene oxide, low M.W. (˜100,000)              G     Polyox WSR-N-205                                                                           Polyethylene oxide, high M.W.                                                 (˜600,000)                                           H     Polyox WSR-N-205                                                                           Polyethylene oxide, medium M.W.                                               (˜300,000)                                           I     FlowPro 1512 Sodium lignosulfonate                                      J     FlowPro 9120 Anionic polymer (AA/AM)                                    K     Betz Polymer 1175                                                                          Cationic polymer (ADA/DETA/EPI)                            L     Betz Polymer 2651                                                                          Cationic polymer (DADMAC/AM)                               M     Betz Polymer 2666                                                                          Cationic polymer (pseudo-star*,                                               50% cationic)                                              N     Betz Polymer 2672                                                                          Cabonic polymer (graft, 5% cationic)                       0     Betz Polymer 2674                                                                          Cationic polymer (graft, 10% cationic)                     P     Betz Polymer 2676                                                                          Cationic polymer (graft, 20% cationic)                     ______________________________________                                         *pseudo-star is a type of block copolymer.                               

                  TABLE II                                                        ______________________________________                                        Gold Ore Agglomeration with 3 lbs. cement/ton ore (pH = 10.7)                 TREATMENTS                                                                              FEED RATES                                                                Cross-               Cross-linking                                                                           %                                              linking Polymer      Agent     Agglomera-                               Polymer                                                                             Agent   (lb. Active/Ton)                                                                           (lb. Active/Ton)                                                                        tion                                     ______________________________________                                        A     --      0.25         --        0                                        D     --      0.25         --        74                                       L     --      0.25         --        76                                       M     --      0.25         --        42                                       N     --      0.25         --        87                                       O     --      0.25         --        87                                       P     --      0.25         --        80                                       K     --      0.25         --        0                                        J     --      0.25         --        94                                       A     Boric   0.25         0.025     0                                              Acid                                                                    D     Boric   0.25         0.025     63                                             Acid                                                                    A     Glyoxal 0.25         0.025     0                                        D     Glyoxal 0.25         0.025     63                                       ______________________________________                                    

                  TABLE III                                                       ______________________________________                                        Gold Ore Agglomeration with 2.0 lbs. lime/ton ore (pH = 10.7)                 TREATMENTS                                                                              FEED RATES                                                                Cross-               Cross-linking                                                                           %                                              linking Polymer      Agent     Agglomera-                               Polymer                                                                             Agent   (lb. Active/Ton)                                                                           (lb. Active/Ton)                                                                        tion                                     ______________________________________                                        A     --      0.25         --        0                                        D     --      0.25         --        66                                       L     --      0.25         --        94                                       M     --      0.25         --        31                                       N     --      0.25         --        93                                       O     --      0.25         --        88                                       P     --      0.25         --        80                                       K     --      0.25         --        0                                        J     --      0.25         --        94                                       A     Boric   0.25         0.025     0                                              Acid                                                                    D     Boric   0.25         0.025     72                                             Acid                                                                    A     Glyoxal 0.25         0.025     0                                        D     Glyoxal 0.25         0.025     61                                       ______________________________________                                    

                  TABLE IV                                                        ______________________________________                                        Gold Ore Agglomeration pH = 2.0                                               TREATMENTS                                                                              FEED RATES                                                                Cross-               Cross-linking                                                                           %                                              linking Polymer      Agent     Agglomera-                               Polymer                                                                             Agent   (lb. Active/Ton)                                                                           (lb. Active/Ton)                                                                        tion                                     ______________________________________                                        A     --      0.25         --        0                                        D     --      0.25         --        85                                       L     --      0.25         --        67                                       M     --      0.25         --        88                                       N     --      0.25         --        76                                       O     --      0.25         --        69                                       P     --      0.25         --        80                                       K     --      0.25         --        0                                        J     --      0.25         --        0                                        A     Boric   0.25         0.025     0                                              Acid                                                                    D     Boric   0.25         0.025     48                                             Acid                                                                    A     Glyoxal 0.25         0.025     0                                        D     Glyoxal 0.25         0.025     60                                       ______________________________________                                    

                  TABLE V                                                         ______________________________________                                        Copper Ore Agglomeration at pH = 2.0                                          TREATMENTS                                                                              FEED RATES                                                                Cross-               Cross-linking                                                                           %                                              linking Polymer      Agent     Agglomera-                               Polymer                                                                             Agent   (lb. Active/Ton)                                                                           (lb. Active/Ton)                                                                        tion                                     ______________________________________                                        A     --      0.25         --        0                                        D     --      0.25         --        0                                        L     --      0.25         --        77                                       M     --      0.25         --        86                                       N     --      0.25         --        82                                       O     --      0.25         --        71                                       P     --      0.25         --        88                                       K     --      0.25         --        0                                        J     --      0.25         --        20                                       A     Boric   0.25         0.025     0                                              Acid                                                                    D     Boric   0.25         0.025     27                                             Acid                                                                    A     Glyoxal 0.25         0.025     0                                        D     Glyoxal 0.25         0.025     29                                       ______________________________________                                    

Tables II and III indicate that several of the tested cationiccopolymers are efficacious in agglomerating gold ore under alkalineconditions relative to treatment J. In Table III, where lime was used toprovide alkalinity to the gold ore, treatments L and N were particularlyeffective.

Table IV shows that all of the cationic polymers with the exception oftreatment K were more effective than treatment J in agglomerating goldore under acidic conditions.

In Table V, polymer feed rates were increased to one pound active perton of ore. Under these conditions, the agglomeration of low pH (pH 2.0)copper ore, cationic polymers treatments M and P were the mosteffective.

While the present invention has been described with respect toparticular embodiments thereof, it is apparent that other forms andmodifications of the invention will be obvious to those skilled in theart. The appended claims and this invention generally should beconstrued to cover all such obvious forms and modifications which arewithin the true spirit and scope of the present invention.

We claim:
 1. In a process for percolation leaching of minerals from amineral bearing ore wherein the ore is first agglomerated with anagglomeration agent, formed into a heap and then leached by percolatinga leaching solution through the heap which extracts the minerals fromthe agglomerated ore for subsequent recovery at an acidic pH, theimprovement in which the agglomerating agent comprises a cationiccopolymer selected from the group consisting of block copolymers of thegeneral structure: ##STR8## wherein J is a polymeric segment obtainedfrom the polymerization of ethylenically unsaturated hydrophobicmonomers initiated by a difunctional initiator; R₄ and R₅ are H or a C₁to C₃ alkyl group; K is a salt of an ammonium cation selected from thegroup consisting of NHR₆ N⁺ (R₇,8,9)M⁻ or OR₆ N⁺ (R₇,8,9)M⁻, wherein R₆is a C₁ to C₄ linear or branched alkylene group, and R₇, R₈ and R₉ canbe selected from the group consisting of hydrogen, C₁ to C₄ linear orbranched alkyl, C₅ to C₈ cycloalkyl, aromatic and alkylaromatic group;and M⁻ is an anion, selected from the group consisting of chloride,bromide, methyl sulfate and hydrogen sulfate; and the molar percentageof x:y is from about 0:100 to 95:5, with the proviso that the total ofx+y equals 100%.
 2. The method of claim 1 wherein the acidic pH is aboutpH 2.0.
 3. The block copolymers of claim 1 wherein the ethylenicallyunsaturated hydrophobic monomer is selected form the group consisting ofalkyl acrylate having from 4 to about 16 carbon atoms, the higher alkylesters of ethylenically unsaturated carboxylic acids other than thealkyl acrylate alkaryl esters of ethylenically unsaturated carboxylicacids, N-alkyl ethylenically unsaturated amides, vinyl alkylates whereinthe alkyl moiety has at least 8 carbon atoms, N-vinyl amides andaralkylstyrenes.
 4. The block copolymer of claim 3 wherein the alkylacrylate is 2-ethylhexyl acrylate.